class_docstr: Zip multiple :class:`~fairseq.data.FairseqDataset` instances together.
  
  Shorter datasets are repeated in a round-robin fashion to match the length
  of the longest one.
  
  Args:
      datasets (Dict[~fairseq.data.FairseqDataset]): a dictionary of
          :class:`~fairseq.data.FairseqDataset` instances.
      eval_key (str, optional): a key used at evaluation time that causes
          this instance to pass-through batches from *datasets[eval_key]*.
class_docstr_tok: ["Zip","multiple",":","class",":","`","~fairseq.data.FairseqDataset","`","instances","together",".","Shorter","datasets","are","repeated","in","a","round-robin","fashion","to","match","the","length","of","the","longest","one",".","Args",":","datasets","(","Dict","[","~fairseq.data.FairseqDataset","]",")",":","a","dictionary","of",":","class",":","`","~fairseq.data.FairseqDataset","`","instances",".","eval_key","(","str",",","optional",")",":","a","key","used","at","evaluation","time","that","causes","this","instance","to","pass-through","batches","from","*","datasets","[","eval_key","]","*","."]
docstr: Ordered indices for batching.
docstr_tok: ["Ordered","indices","for","batching","."]
code: def ordered_indices(self):
      """Ordered indices for batching."""
      if self._ordered_indices is None:
          # Call the underlying dataset's ordered_indices() here, so that we
          # get the same random ordering as we would have from using the
          # underlying sub-datasets directly.
          self._ordered_indices = OrderedDict(
              [
                  (key, dataset.ordered_indices())
                  for key, dataset in self.datasets.items()
              ]
          )
      return np.arange(len(self))
  
file_path: fairseq/fairseq/data/round_robin_zip_datasets.py
imports: import logging
  from collections import OrderedDict
  from typing import Dict, Sequence
  import numpy
  from .None import FairseqDataset, LanguagePairDataset
label_desc: Use image node_id 8 for calling the RoundRobinZipDatasets obj's underlying member method code with example usage: obj.ordered_indices() and returns: np